Radio link monitoring in shared spectrum

ABSTRACT

A WTRU may be configured to perform radio link monitoring (RLM) based on RLM reference signals (RLM-RSs) transmitted in a cell operating in an unlicensed spectrum. The WTRU may evaluate a radio link failure (RLF) status for the cell using a first RLM criteria based on the RLM-RSs. A transmission instance of the RLM-RSs may be skipped, for example, due to a listen before talk (LBT) failure at a gNodeB (gNB). The WTRU may adapt or change the first RLM criteria and/or evaluate the RLF status of the cell operating in the unlicensed spectrum using a second RLM criteria based on determining that the transmission instance of the RLM-RSs was skipped. The first RLM criteria may correspond to a first RLM process that utilizes a first set of RLM parameters. The second RLM criteria may correspond to a second RLM process that utilizes a second set of RLM parameters.

CROSS-REFERENCE TO RELATED CASES

The present application claims the benefit of U.S. Provisional PatentApplication No. 62/686,758, filed Jun. 19, 2018, U.S. Provisional PatentApplication No. 62/715,641, filed Aug. 7, 2018, and U.S. ProvisionalPatent Application No. 62/790,183, filed Jan. 9, 2019, the contents ofwhich are hereby incorporated by reference in their entireties.

BACKGROUND

Mobile communications using wireless communication continue to evolve. Afifth generation may be referred to as 5G. A previous (legacy)generation of mobile communication may be, for example, fourthgeneration (4G) long term evolution (LTE).

SUMMARY

Systems, methods, and instrumentalities for radio link monitoring inshared spectrum may be disclosed herein. A wireless transmit receiveunit may be configured to determine a channel status. For example, achannel status may correspond to a relative state of the channel, suchas one or more of clear (e.g., high quality, low usage, etc.), busy(e.g., frequent usage, good or bad quality when available, etc.),bad/poor (e.g., low quality even when channel usage is low), etc.

A wireless transmit/receive unit (WTRU) may be configured to utilizetechniques to determine or otherwise differentiate between a bad channel(e.g., poor channel conditions) and a busy channel (e.g., high usageand/or interference levels in a channel with otherwise acceptablechannel conditions). The WTRU may evaluate the channel and identify alevel of uncertainty and/or ambiguity when processing measurementsamples as to whether measurements correspond to a bad channel, a poorchannel, and/or both.

A WTRU may be configured to perform radio link monitoring (RLM)measurements in a cell. The cell may transmit radio link monitoringreference signals (RLM-RSs) in an unlicensed spectrum. A WTRU may beconfigured to perform RLM measurements based on the RLM-RSs. The WTRUmay measure the RLM-RSs. The WTRU may evaluate a radio link failure(RLF) status for the cell using a first RLM criteria based ondetermining that a transmission instance of the RLM-RSs was transmittedin the cell. For example, the WTRU may evaluate the RLF status for thecell using the first RLM criteria based on measuring the RLM-RSs. Atransmission instance of the RLM-RSs may be skipped, for example, due toa listen before talk (LBT) failure of a gNodeB (gNB). The WTRU maydetermine that a transmission instance of the RLM-RSs was skipped. TheWTRU may adapt or change the first RLM criteria and/or evaluate the RLFstatus of the cell operating in the unlicensed spectrum using a secondRLM criteria based on determining that the transmission instance of theRLM-RSs was skipped. The first RLM criteria may correspond to a firstRLM process that utilizes a first set of RLM parameters. The second RLMcriteria may correspond to a second RLM process that utilizes a secondset of RLM parameters.

The WTRU may be indicated or determine that the transmission instance ofthe RLM-RSs was skipped. For example, the WTRU may be configured toreceive an indication from the gNB that indicates that the transmissioninstance of the RLM-RSs was skipped.

The WTRU may be configured to determine that the transmission instanceof the RLM-RSs was skipped based on one or more detected or implicitcriteria. For example, the WTRU may fail to detect a characteristicassociated with the RLM-RSs during the transmission instance. The WTRUmay determine that the transmission instance of the RLM-RSs was skippedbased on failing to detect the characteristic associated with theRLM-RSs during the transmission instance. The characteristic may includeone or more of a scrambling identification (ID) associated with theRLM-RSs, a cyclic shift, and/or the like. The WTRU may be configured tomeasure a received signal strength indicator (RSSI) of a resource of thecell. The WTRU may determine that the measured RSSI is greater than athreshold. The WTRU may be configured to determine that the transmissioninstance of the RLM-RSs was skipped based on the determination that themeasured RSSI is greater than the threshold. The WTRU may be configuredto measure a power on one or more resource elements that are blanked bythe gNB. The WTRU may determine that the measured power is above athreshold. The WTRU may be configured to determine that the transmissioninstance of the RLM-RSs was skipped based on the determination that themeasured power is above the threshold. The WTRU may be configured todetermine that the transmission instance of the RLM-RSs was skippedbased on a condition or a combination of conditions. For example, theWTRU may be configured to determine that the transmission instance ofthe RLM-RSs was skipped when the RSSI in the resource elementsassociated with RLM-RS is above a first threshold and the RSRP of theresource elements associated with RLM-RS is below a second threshold.

The first RLM criteria and the second RLM criteria may be different. Thesecond RLM criteria may include the use of a no-sync (NS) indication,for example, when an RLM-RS is determined (e.g., by the WTRU) to be notreceived. The second RLM criteria may include a counter of no-sync (NS)indications. The second RLM criteria may include a fractional counter ofout-of-sync (OOS) indications. The second RLM criteria may include afractional increment of an OOS counter. The first RLM criteria and thesecond RLM criteria may include different conditions requiring a numberof consecutive OOS indications to declare RLF. For example, the numberof consecutive OOS indications required in the second RLM criteria maybe greater than the first number of consecutive OOS indications requiredin the first RLM criteria.

The second RLM criteria may include a calculation of a block error rate(BLER). For example, the WTRU may be configured to calculate the BLER byapplying a negative offset increment on the BLER for an indicationinterval. The WTRU may be configured to compare the calculated BLER witha threshold. The WTRU may be configured to generate at least one of anOOS indication, an in-sync (IS) indication, or an NS indication based onthe comparison.

The WTRU may be configured to perform LBT in the cell in the unlicensedspectrum. The WTRU may defer a number of uplink (UL) transmissions. TheWTRU may determine that a number of deferred UL transmissions exceeds athreshold. The WTRU may send an indication of RLF based on thedetermination that the number of the deferred UL transmissions exceedsthe threshold. The WTRU may determine that UL access latency exceeds athreshold. The WTRU may send an indication of RLF based on thedetermination that the UL access latency exceeds the threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A according to an embodiment.

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an embodiment.

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A according to an embodiment.

FIG. 2 illustrates an example of a WTRU using a modified RLMimplementation.

FIG. 3 illustrates an example flowchart that may be part of an RLMimplementation.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN104/113, a CN 106/115, a public switched telephone network (PSTN) 108,the Internet 110, and other networks 112, though it will be appreciatedthat the disclosed embodiments contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d may be any type of device configured to operateand/or communicate in a wireless environment. By way of example, theWTRUs 102 a, 102 b, 102 c, 102 d, any of which may be referred to as a“station” and/or a “STA”, may be configured to transmit and/or receivewireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106/115, the Internet110, and/or the other networks 112. By way of example, the base stations114 a, 114 b may be a base transceiver station (BTS), a Node-B, an eNodeB, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller,an access point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104/113, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals on one or morecarrier frequencies, which may be referred to as a cell (not shown).These frequencies may be in licensed spectrum, unlicensed spectrum, or acombination of licensed and unlicensed spectrum. A cell may providecoverage for a wireless service to a specific geographical area that maybe relatively fixed or that may change over time. The cell may furtherbe divided into cell sectors. For example, the cell associated with thebase station 114 a may be divided into three sectors. Thus, in oneembodiment, the base station 114 a may include three transceivers, i.e.,one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and mayutilize multiple transceivers for each sector of the cell. For example,beamforming may be used to transmit and/or receive signals in desiredspatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104/113 and the WTRUs 102 a,102 b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 115/116/117 using wideband CDMA (WCDMA).WCDMA may include communication protocols such as High-Speed PacketAccess (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-SpeedDownlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., a eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106/115.

The RAN 104/113 may be in communication with the CN 106/115, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. The data may have varying qualityof service (QoS) requirements, such as differing throughputrequirements, latency requirements, error tolerance requirements,reliability requirements, data throughput requirements, mobilityrequirements, and the like. The CN 106/115 may provide call control,billing services, mobile location-based services, pre-paid calling,Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication. Although notshown in FIG. 1A, it will be appreciated that the RAN 104/113 and/or theCN 106/115 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 104/113 or a different RAT. Forexample, in addition to being connected to the RAN 104/113, which may beutilizing a NR radio technology, the CN 106/115 may also be incommunication with another RAN (not shown) employing a GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106/115 may also serve as a gateway for the WTRUs 102 a, 102 b,102 c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104/113 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) anddownlink (e.g., for reception) may be concurrent and/or simultaneous.The full duplex radio may include an interference management unit toreduce and or substantially eliminate self-interference via eitherhardware (e.g., a choke) or signal processing via a processor (e.g., aseparate processor (not shown) or via processor 118). In an embodiment,the WRTU 102 may include a half-duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for either the UL (e.g., for transmission) or thedownlink (e.g., for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (or PGW) 166. While each of the foregoing elements are depictedas part of the CN 106, it will be appreciated that any of these elementsmay be owned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In certain representative embodiments, the DLS may use an 802.11e DLS oran 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS)mode may not have an AP, and the STAs (e.g., all of the STAs) within orusing the IBSS may communicate directly with each other. The IBSS modeof communication may sometimes be referred to herein as an “ad-hoc” modeof communication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In certainrepresentative embodiments, Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA) may be implemented, for example in in 802.11systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed/detectedand/or determined to be busy by a particular STA, the particular STA mayback off. One STA (e.g., only one station) may transmit at any giventime in a given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications, such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 113 and the CN 115according to an embodiment. As noted above, the RAN 113 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 113 may also be in communication with theCN 115.

The RAN 113 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 113 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containingvarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, dual connectivity, interworkingbetween NR and E-UTRA, routing of user plane data towards User PlaneFunction (UPF) 184 a, 184 b, routing of control plane informationtowards Access and Mobility Management Function (AMF) 182 a, 182 b andthe like. As shown in FIG. 1D, the gNBs 180 a, 180 b, 180 c maycommunicate with one another over an Xn interface.

The CN 115 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whileeach of the foregoing elements are depicted as part of the CN 115, itwill be appreciated that any of these elements may be owned and/oroperated by an entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different PDU sessions with differentrequirements), selecting a particular SMF 183 a, 183 b, management ofthe registration area, termination of NAS signaling, mobilitymanagement, and the like. Network slicing may be used by the AMF 182 a,182 b in order to customize CN support for WTRUs 102 a, 102 b, 102 cbased on the types of services being utilized WTRUs 102 a, 102 b, 102 c.For example, different network slices may be established for differentuse cases such as services relying on ultra-reliable low latency (URLLC)access, services relying on enhanced massive mobile broadband (eMBB)access, services for machine type communication (MTC) access, and/or thelike. The AMF 162 may provide a control plane function for switchingbetween the RAN 113 and other RANs (not shown) that employ other radiotechnologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP accesstechnologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN115 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 115 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingdownlink data notifications, and the like. A PDU session type may beIP-based, non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering downlink packets, providing mobility anchoring, and thelike.

The CN 115 may facilitate communications with other networks. Forexample, the CN 115 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 115 and the PSTN 108. In addition, the CN 115may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a localData Network (DN) 185 a, 185 b through the UPF 184 a, 184 b via the N3interface to the UPF 184 a, 184 b and an N6 interface between the UPF184 a, 184 b and the DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

The term “network” as used herein may refer to one or more gNBs, whichmay be associated with one or more transmission/reception points (TRPs)or any other node in a radio access network. PDU may refer to protocoldata unit.

The term “shared spectrum” as used herein may refer to any spectrum thatis shared between multiple operators and/or multiple technologies, forexample 3GPP, WiFi, radar, satellite, and the like. “Shared spectrum” asused herein may include lightly licensed spectrum, licensed spectrumthat is shared between operators, and/or unlicensed spectrum. The terms“shared” and “unlicensed” may be used interchangeably herein. Althoughthe techniques described herein may be applicable to shared spectrumscenarios, the techniques may have applicability to non-shared spectrum.The examples should not be interpreted to only shared spectrumdeployments unless specifically noted herein.

Next-generation air interfaces, including further evolution of LTEAdvanced Pro and New Radio (NR), may support a wide range of use caseswith varying service requirements. For example, low-overheadlow-data-rate power-efficient services (e.g., mMTC), ultra-reliablelow-latency services (e.g., URLLC), and/or high-data-rate mobilebroadband services (e.g., eMBB) may be supported. Diverse wirelesstransmit/receive unit (WTRU) capabilities may be supported. For example,low-power low-bandwidth WTRUs, WTRUs that are capable of very widebandwidth (e.g., 80 MHz), and/or WTRUs with support for high frequencies(e.g., greater than 6 GHz) may be supported. Different spectrum usagemodels may be supported. For example, stationary/fixed and/or high speedtrain scenarios may be supported. Architecture that is flexible enoughto adapt to diverse deployment scenarios may be used. For example, oneor more of standalone, non-standalone (e.g., with assistance fromanother air interface), centralized, virtualized, and/or distributedover ideal/non-ideal backhaul architectures may be used.

A WTRU may operate using bandwidth parts (BWPs) in a carrier, e.g., inNR. A WTRU may access a cell that uses a (e.g., initial) BWP. The WTRUmay be configured with a set of BWPs, for example, to continueoperation. For example, a WTRU may have one active BWP at any givenmoment. A BWP (e.g., each BWP) may be configured with a set of controlresource sets (CORESETs). A WTRU may blind decode physical downlinkcontrol channel (PDCCH) candidates for scheduling within a CORESET.

NR may support variable transmission duration(s) and/or feedback timing.A physical downlink shared channel (PDSCH) and/or physical uplink sharedchannel (PUSCH) transmission may occupy a subset (e.g., contiguoussubset) of symbols of a slot. The subset of symbols may be associatedwith variable transmission duration(s). A downlink control information(DCI) for a DL assignment may include an indication of timing offeedback for a WTRU (e.g., by pointing to a specific PUCCH resource),for example with variable feedback timing.

NR may support multiple types of physical uplink control channel (PUCCH)resources. For example, NR may support a short PUCCH and a long PUCCH. Ashort PUCCH may be transmitted using 1 or 2 OFDM symbols. A long PUCCHmay be transmitted using, for example, 14 orthogonal frequency-divisionmultiplexing (OFDM) symbols. PUCCH types (e.g., each PUCCH type) mayhave multiple formats. The formats may depend on a type and/or a size ofa corresponding payload.

Beamforming may be used to compensate for increased pathloss at higherfrequencies (e.g., greater than 6 GHz). A relatively large number ofantenna elements may be used to achieve a higher beamforming gain.

Analog and/or hybrid beamforming may be used to reduce implementationcosts (e.g., to reduce a number of RF chains). Analog and/or hybridbeams may be multiplexed in time. Beamforming may be applied for one ormore of Sync, PBCH, or Control channels, for example to provide cellwide coverage. The term “beam sweep” as used herein may refer totransmission and/or reception of beamformed channels (e.g., multiplexedin time and/or frequency and/or space.

The term “reference signal” as used herein may refer to a signal,preamble, or system signature that may be received and/or transmitted bya WTRU (e.g., for one or more purposes as described herein). Differentreference signals may be defined for beam management in DL and/or UL.For example, downlink beam management may use one or more of channelstate information reference signal (CSI-RS), demodulation referencesignal (DMRS), synchronization signal, or the like. Uplink beammanagement may use one or more of sounding reference signal (SRS), DMRS,random-access channel (RACH), or the like.

Operation may occur in a shared spectrum deployment. Operation in anunlicensed frequency band may be subject to limits on one or more oftransmit power control (TPC), radio frequency (RF) output power, orpower density (e.g., as given by mean effective isotropic radiated power(EIRP) and/or mean EIRP density at the highest power level). Operationin an unlicensed frequency band may be subject to requirements on atransmitted out of band emission(s). The requirements may be specific tobands and/or geographical locations.

Operation in an unlicensed frequency band may be subject to requirementsof the Nominal Channel Bandwidth (NCB) and/or the Occupied ChannelBandwidth (OCB). OCB may be defined for unlicensed spectrum in the 5 GHzregion. For example, the NCB may be the widest band of frequenciesinclusive of guard bands assigned to a single channel. The NCB may be atleast 5 MHz. The OCB may include the bandwidth containing 99% of thepower of the signal. The OCB may be between 80% and 100% of the declaredNCB. A device may be allowed to operate temporarily in a mode where thedevice's OCB is reduced, for example, during an establishedcommunication. the device's OCB may be reduced to as low as 40% of thedevice's NCB (e.g., with a minimum of 4 MHz).

Channel access in an unlicensed frequency band may use aListen-Before-Talk (LBT). LBT may be mandated (e.g., independently of)whether the channel is occupied.

LBT may be characterized, for example, for frame-based systems. LBT maybe characterized by one or more of a Clear Channel Assessment (CCA) time(e.g., ˜20 μs), a Channel Occupancy time (e.g., minimum 1 ms, maximum 10ms), an idle period (e.g., minimum 5% of channel occupancy time), afixed frame period (e.g., equal to the channel occupancy time+idleperiod), a short control signaling transmission time (e.g., maximum dutycycle of 5% within an observation period of 50 ms), or a CAA energydetection threshold.

LBT may be characterized, for example, for load-based systems. Inload-based systems, transmit/receive structure may not be fixed in time.LBT may be characterized by a number N corresponding to a number ofclear idle slots in an extended CCA (e.g. instead of the fixed frameperiod). N may be selected randomly within a range.

Deployment scenarios may include different standalone NR-basedoperations, different variants of dual connectivity operation and/ordifferent variants of carrier aggregation (CA). Variants of dualconnectivity operation may include one or more of EN-DC with at leastone carrier operating according to the LTE radio access technology (RAT)or NR DC with at least two set of one or more carriers operatingaccording to the NR RAT. Variants of CA may include differentcombinations of zero or more carriers of each of LTE and NR RATs.

A listen-before-talk (LBT) may be used by an equipment where theequipment applies a clear channel assessment (CCA) check before using achannel. The CCA may utilize energy detection and/or other approaches todetermine the presence or absence of other signals on a channel, forexample, in order to determine if a channel is occupied or clear,respectively. Usage of LBT in the unlicensed bands may be mandated.Carrier sensing (e.g., via LBT) may be a way for fair sharing ofunlicensed spectrum. Carrier sensing (e.g., via LBT) may be consideredto be a vital feature for fair and/or friendly operation in theunlicensed spectrum in a single global solution framework.

Discontinuous transmission may occur on a carrier with limited maximumtransmission duration. In an unlicensed spectrum, channel availabilitymay not be guaranteed. Continuous transmission may be prohibited. Limitson the maximum duration of a transmission burst in the unlicensedspectrum may be imposed. Discontinuous transmission with the limitedmaximum transmission duration may be a functionality for licenseassisted access (LAA).

Carrier selection may occur. Carrier selection may be used for LAA nodesto select carriers (e.g., with low interference and that achieveco-existence with other unlicensed spectrum deployments). There may be alarge available bandwidth of unlicensed spectrum.

TPC may be a requirement by which a transmitting device may be able toreduce transmit power (e.g., in a proportion of 3 dB or 6 dB) comparedto a maximum nominal transmit power.

Radio resource management (RRM) measurements (e.g., including cellidentification) may occur. RRM measurements (e.g., including cellidentification) may enable mobility between SCells and/or robustoperation in an unlicensed band.

CSI measurement (e.g., including channel and/or interference) may occur.A WTRU operating in an unlicensed carrier may support frequency/timeestimation and/or synchronization, for example, to enable RRMmeasurements and/or for successful reception of information on theunlicensed band.

A transmission instance of RLM-RS may be interfered or skipped. Theinterfered or skipped transmission instance of RLM-RS may be due to anLBT failure (e.g., of a gNB). Transmissions in an unlicensed spectrummay be preceded by a LBT period or procedure (e.g., at an gNB).Performing an LBT may enable a co-existence with 3GPP and non-3GPPneighbors (e.g., WiFi). RLM (e.g., an RLM process) may rely on periodictransmissions of reference signals. The reference signals may include,for example, an RLM-RS(s). When used herein, the term RLM-RS(s) mayrefer to any reference signals used by a WTRU to monitor radio linkconditions. For example, RLM-RS(s) may correspond to one or moresynchronization signals; or blocks, one or more CSI-RSs, and/or othertypes of reference signals.

In some communication scenarios—for example an unlicensedspectrum—periodic transmissions of an RLM-RS(s) may not be guaranteed.For example, RLM-RS transmissions may be subject to transmissionuncertainty since the channel may already be occupied which could resultin a failed LBT. For example, upon failure of LBT (e.g., due to thechannel being occupied by another user or another radio accesstechnology), a transmission instance of RLM-RS(s) may be skipped. A WTRUmay or may not treat an absence of RLM-RS(s) as an out-of-sync (OOS)condition, for example depending on its configured mode and/or otherobserved criterion. As an example, a WTRU may fail to detect an RLM-RStransmission due to an interference from a hidden node.

The WTRU may determine a temporary interference condition as an OOScondition. An OOS indication may be triggered during a busy channel. TheOOS indication triggered during the busy channel may not be indicativeof a channel quality. The OOS indication triggered during the busychannel may result in transient changes to a perceived cell coverage(e.g., at the WTRU). The WTRU may trigger radio link failure (RLF)and/or may re-establish to the same cell. Interruptions, data loss,and/or unnecessary signaling may ensue. A large number of WTRUs on thenetwork may trigger re-establishment during busy channel conditions, forexample, causing a signaling storm. RLM may be enhanced to handle RLM-RStransmissions that may be subject to transmission uncertainty.

A WTRU may be configured to use a modified RLM process, RLM criteria,and/or set of RLM parameters for RLM. For example, an RLM process may bemodified in order to differentiate bad channels from busy channels. AWTRU may detect a level of uncertainty and/or ambiguity that may existwhen the WTRU processes measurement samples. A WTRU may influence (e.g.,modify, adjust, or adapt) RLM based on, for example, a channel status.An RLM process may include processing, handling, and/or reacting to anambiguous channel (e.g., a channel that may be busy, may be poor, or maybe both). A WTRU behavior may be configured and/or controlled, e.g.,when the WTRU is performing RLM in a shared spectrum.

As an example, determining whether a RLF has occurred and/or actions totake based on an RLF declaration may depend on whether the WTRU hasdetected a poor channel or a busy channel. For example, first RLMcriteria (e.g., such as a number of consecutive out-of-sync conditions)may be used to determine RLF has occurred due to a poor channel. SecondRLM criteria (e.g., such as a number of consecutive skipped RLM RStransmissions and/or a consecutive number of no-sync indications) may beused to determine RLF has occurred due to a busy channel. In someexamples, declaring RLF based on a busy channel or based on a poorchannel may result in the same actions being performed by the WTRU(e.g., the WTRU reacts in the same way to RLF declared based on busychannel as it would for a poor channel). In other example, the WTRU mayreact differently to an RLF declaration due to a busy channel than to anRLF declaration based on a poor channel.

A WTRU may use channel status information to influence (e.g., modify,adjust, or adapt) RLM. Deployments in an unlicensed spectrum may becharacterized by sharing a frequency band. For example, two or moreoperators may share a frequency band and may or may not be coordinated.Two or more 3GPP (e.g. LTE/NR) and/or non-3GPP wireless systems (e.g.WiFi or radar) may share a frequency band, and may or may not becoordinated. A reference signal (e.g., one relevant to RLM) may not betransmitted when a channel is busy. A transmitted reference signal maybe masked by an interfering transmission(s), for example, from a hiddennode. Reference signal measurements may be ambiguous (e.g., referred asambiguous channel). A WTRU may not be able to determine the nature ofconnectivity to a source cell, for example, in an ambiguous channel. Forexample, a channel(s) may be of ambiguous when a WTRU performsmeasurements but is unable to determine whether a channel has poormeasurements because the channel is busy or because the channel itselfis poor from the perspective of the WTRU. The channel may be busy if thechannel could be of acceptable quality but is being used by anothertechnology or source at the time of measurements. The channel itself maybe poor from the perspective of the WTRU if the channel was not beingused during the measurements but is still of a poor quality. Channelstatus information may be obtained and/or determined, for example, todetermine the nature of connectivity to a source cell in an ambiguouschannel.

A WTRU may use channel status information to influence one or moreaspects of radio link monitoring. The channel status information may beobtained from, for example, LBT or CCA or other signaling from network.The WTRU may perform different actions in channels with differentchannel qualities (e.g., good, busy/ambiguous, or bad channelqualities), for example, based on a result of channel status aware RLM.The different channel qualities may include good, busy/ambiguous, or badchannel qualities. For example, the WTRU may not treat a busy and/orambiguous channel at the same level of severity as a bad channel.

Implementations described herein may be applicable to functions (e.g.,RLM, beam failure detection, and/or the like) involved in evaluating theconnectivity to the network in a wireless system, for example LTE and/orNR.

A WTRU may be configured to determine a channel status. For example, thechannel status may be based on a determination as to whether atransmission instance of RLM-RS was skipped or whether the RLM-RS wastransmitted but the WTRU measures a poor channel based on the RLM-RS. AWTRU may differentiate bad channel from a busy channel or at leastdetect some level of uncertainty/ambiguity. For example, a channelstatus may correspond to a relative state of the channel (e.g., one ormore of clear, busy, bad/poor etc.). A state of the channel may berelatively clear (e.g., high quality, low usage, etc.). A state of thechannel may be relatively busy (e.g., frequent usage, good or badquality when available, etc.). A state of the channel may be relativelybad/poor (e.g., low quality even when channel usage is low). The WTRUmay evaluate the channel as to whether measurements correspond to a badchannel and/or a poor channel, for example, when processing measurementsamples. The WTRU may identify a level of uncertainty and/or ambiguityas to whether measurements correspond to a bad channel and/or a poorchannel, for example, when processing measurement samples. The WTRU maybe configured to determine a channel status associated with a servingcell. The WTRU may use information about the channel status during RLM.The WTRU may determine that at least one transmission instance of RLM-RSwas skipped. For example, the channel status information may implicitlyor explicitly indicate whether a transmission instance of RLM-RS wasskipped due to a busy channel. The channel status information mayimplicitly or explicitly indicate whether an interference (e.g., from ahidden node) is masking an RLM-RS transmission.

A received signal strength indicator(s) (RSSI(s)) may be measured and/orused to determine a channel status (e.g., whether a transmissioninstance of RLM-RS was skipped). A WTRU may be configured to performClear Channel Assessment (CCA) during RLM. For example, the WTRU may beconfigured to measure RSSI in a time window (e.g., a predefined timewindow). The WTRU may be configured to measure RSSI in symbols (e.g.,symbols associated with a RLM-RS transmission(s)). A relatively highRSSI value may be indicative of an interference(s), e.g., from anon-serving node. For example, the WTRU may consider that the channel isbusy or ambiguous if the downlink quality associated with the RLM-RS isbelow a threshold and/or the RSSI is above a threshold. The WTRU maydetermine that a transmission instance of RLM-RS was skipped based on ameasurement of RSSI that is greater than the threshold.

A Zero-Power RS (ZP-RS) may be measured and/or used to determine achannel status (e.g., whether a transmission instance of RLM-RS wasskipped). A WTRU may be configured with one or more ZP-RSs (e.g., ZP-RSconfigurations). The ZP-RS(s) may be associated with a resource(s)(e.g., correspond to resource elements) that a gNB blanks. The WTRU mayexpect a blank transmission(s) from a serving gNB in the resource(s).The WTRU may be configured to measure power in the resource(s) (e.g.,resource elements) associated with the ZP-RS. The ZP-RS and a RLM-RS(s)may be configured in the same resources (e.g., symbols or subframes).For example, the ZP-RS and the RLM-RS(s) may be configured in the sameresource block(s), sub-band(s), and/or BWP(s). A configured RLM-RS and aZP-RS may be associated (e.g., linked). An association (e.g., a linkage)between the configured RLM-RS and the ZP-RS may be used, for example, toevaluate the interference associated with a specific resource. Thenon-zero power in a ZP-RS may be indicative of interferences (e.g., froma non-serving node). The WTRU may consider that the channel is busy orambiguous if the received power in the ZP-RS is above a threshold. Forexample, a WTRU may measure a power on one or more resource elementsconfigured to be blanked by a gNB. The WTRU may determine that atransmission instance of RLM-RS was skipped based on a measurement poweron the resource elements that is above a threshold.

A WTRU may be configured to obtain further information about aninterference source. For example, a WTRU may receive a configuration ofone or more ZP-RS(s) that may be used to derive information regarding aninterference source. For example, if a ZP-RS configuration is servingcell specific, then a detected and/or received power in the ZP-RSconfiguration (e.g., a ZP-RS in the ZP-RS configuration) may indicatenon-serving cell interference. The ZP-RS(s) and/or ZP-RS configurationmay be specific to cells belonging to the same operator and/or nodesthat can be coordinated. If the ZP-RS is specific to cells belonging tothe same operator (e.g., that can be coordinated), the detected and/orreceived power in ZP-RS may indicate uncoordinated interference. If theZP-RS is specific to cells belonging to nodes that can be coordinated,the detected and/or received power in ZP-RS may indicate uncoordinatedinterference. The ZP-RS may be specific to 3GPP nodes. If the ZP-RS isspecific to 3GPP nodes, the detected and/or received power in ZP-RS mayindicate interference from a non-3GPP node(s) (e.g., a WiFi access pointor radar).

Retroactive compensation may be used to determine a channel status(e.g., whether a transmission instance of RLM-RS was skipped). Forexample, the WTRU may receive a signal indicating that a previouslyexpected RLM-RS was skipped. The WTRU may receive information indicatingthat a transmission instance of RLM-RS was skipped from a gNB. The WTRUmay receive information at a time (e.g., T) about the status of one ormore RLM-RS transmission instances in the past (e.g. T-n, T-2n etc.).For example, a gNB may skip a transmission(s) of one or more RLM-RS(s).The skipped transmission instance of RLM-RS may be due to LBT failure. AWTRU may receive the information (e.g., indication that indicates theskipped transmission instance of the RLM-RS) in a signaling. A WTRU mayreceive the information after the gNB reacquires the channel fortransmission. The WTRU may determine that one or more RLM-RStransmissions in the past were skipped, for example, based on theinformation.

The WTRU may be configured to update an RLM criteria(ion)), RLMprocess(es), and/or set of RLM parameters (e.g., that is used toevaluate an RLF status of a cell) based on information indicating that atransmission instance of RLM-RS was skipped. The WTRU may be configuredto update an RLM criteria, RLM process, and/or set of RLM parametersbased on the information as described herein. In examples, the WTRU mayperform RLM measurements on RLM-RS(s) that are transmitted on a cell.The cell may operate in an unlicensed spectrum. The WTRU may evaluate anRLF status for the cell, for example, using a RLM criteria. The WTRU maysuccessfully measure the RLM-Rs(s) that are transmitted on the cell. TheRLM criteria may correspond to an RLM process that uses a set of RLMparameters. In an example, the gNB may skip a transmission instance ofRLM-RS (e.g., due to an LBT failure). In this example, if a retroactivecompensation is not used, the WTRU may assume that the RLM-RS wastransmitted and not received by the WTRU, thus generating an OOSindication. A retroactive compensation may be used to update an RLMcriteria, RLM process, and/or set of RLM parameters. The WTRU maydetermine that a transmission instance of the RLM-RSs is skipped, forexample, based on the information indicating that the transmissioninstance of RLM-RS was skipped (e.g., an indication). The WTRU mayupdate the RLM criteria. The updated RLM criteria may correspond to anupdated RLM process that uses an updated set of RLM parameters. Forexample, a first RLM criteria may be based on an N310 counter and/orT310 timer. The WTRU may evaluate an RLF status for a cell operating inan unlicensed spectrum using the first RLM criteria (e.g., where theN310 counter and/or T310 timer may be running). The WTRU may evaluatethe RLF status for the cell operating in the unlicensed spectrum using asecond RLM criteria, for example, where the N310 counter and T310 timermay be decremented (e.g., if running). The first criteria may include afirst condition that requires a first number of consecutive OOSindications to declare RLF. The second RLM criteria may include a secondcondition requiring a second number of consecutive OOS indications todeclare RLF. The second number of consecutive OOS indications may begreater than the first number of consecutive OOS indications.

FIG. 2 illustrates an example of a WTRU using a modified RLMimplementation. In FIG. 2, a WTRU may use a modified or adapted RLMimplementation based on a channel status. The modified or adapted RLMimplementation may be performed based on a channel status. A gNB mayperiodically transmit an RLM-RS on a channel, for example at an RLM-RSperiodicity. As shown in FIG. 2, the gNB may transmit RLM-RS 204 andRLM-RS 206. The WTRU may successfully receive RLM-RS 204 and RLM-RS 206.The WTRU may generate IS indications respectively when the WTRUsuccessfully receives RLM-RS 204 and RLM-RS 206. The gNB may transmitthe RLM-RS 204 and RLM-RS 206 at a periodicity. The periodicity may beshown by the distance between RLM-RS 204 and RLM-RS 206 in time domain.The channel may be an unlicensed channel. The gNB may perform LBT beforetransmitting an RLM-RS. The gNB may fail to transmit the RLM-RS if LBTfails. As shown in FIG. 2, the gNB may have an LBT failure and/or mayskip a transmission of RLM-RS 208. The WTRU may determine that atransmission instance of RLM-RS was skipped and/or generate an OOSindication. The gNB may have an LBT failure and/or may skip atransmission of RLM-RS 210. The gNB may have an LBT failure and/or mayskip a transmission of RLM-RS 212. The WTRU may determine that thetransmission instances of RLM-RS 210 and 212 were skipped and/orgenerate corresponding OOS indications. Next, the gNB does not have anLBT failure and/or may transmit RLM-RS 224. The WTRU may successfullyreceive RLM-RS 224 and generate a corresponding IS indication. The gNBmay have an LBT failure and/or may skip a transmission of RLM-RS 214.The WTRU may determine that a transmission instance of RLM-RS wasskipped and/or generate a corresponding OOS indication. Next, the gNBmay not have an LBT failure and/or may transmit RLM-RSs 216-220. TheWTRU may successfully receive RLM-RSs 216-220 and generate correspondingIS indications.

A WTRU may perform RLM using an RLM criteria, an RLM process, or a setof RLM parameters. For example, the RLM parameters may includetimers/counters, sync indications, etc. The WTRU may fail to receive theRLM-RS because, for example, LBT has failed (e.g., as shown in FIG. 2),or due to interference from a hidden node. If the WTRU fails to receivethe RLM-RS, the WTRU may use an adapted or modified RLM criteria, RLMprocess or set of RLM parameters. As shown in FIG. 2, the WTRU may use afirst set of RLM criteria 226 when the WTRU receives RLM-RSs 204 and206. The WTRU may adapt the RLM criteria or RLM process (e.g., use asecond RLM criteria or RLM process 228) if the WTRU determines a skippedRLM-RS 208. For example, the WTRU may modify the RLM process by changingRLM counters/timers as a function of channel occupancy, modifying IN/OUTsync counting, applying a historical BLER value with a decay factor,etc. The WTRU may modify IN/OUT sync counting by introducing a No-Syncindication or fractionally incrementing an OOS counter when WTRUdetermines that the RLM-RS is skipped. The WTRU may use the RLM criteriaand/or RLM process that the WTRU uses before the WTRU makes theadaptation/modification, for example, if the WTRU successfully receivesan RLM-RS(s). As shown in FIG. 2, the WTRU may use RLM criteria or RLMprocess 230 if the WTRU determines that the WTRU successfully receivesone or more RLM-RSs (e.g., RLM-RS 224). The RLM criteria or RLM process230 may be the same as the first RLM criteria or first RLM process 226.

FIG. 3 illustrates an example flowchart that may be part of an RLMimplementation. A WTRU may monitor a channel for an RLM-RS. For example,the WTRU may evaluate an RLF status based on successfully measuringRLM-RSs. The channel may be an unlicensed channel. The WTRU maydetermine whether an RLM-RS was present (e.g., within a time window). Ifthe RLM-RS was present, the WTRU may use an RLM implementation andcontinue to monitor for an RLM-RS on the channel. If the RLM-RS was notpresent, the WTRU may adapt or modify the RLM implementation and/orperform RLM using the adapted or modified RLM implementation. The WTRUmay return to the RLM implementation, for example, upon receipt of theRLM-RS. The RLM implementation may include one or more of a RLMcriteria, RLM process, or a set of RLM parameters.

The WTRU may receive information indicating that a transmission instanceof RLM-RS was skipped via signaling. The signaling may not specify aRLM-RS periodicity or resource (e.g., may be generic). For example, thesignaling may indicate whether the gNB was transmitting or not during atime (e.g., predefined time periods). The signaling may include (e.g.,be expressed as) a bitmap at the granularity of slots, subframes, and/orframes. The WTRU may determine (e.g., compute) a status of an RLM-RStransmission instance based on, for example, RLM-RS periodicity and/orresource mapping.

The WTRU may receive the signaling of the information indicating that atransmission instance of RLM-RS was skipped via broadcast signaling or adedicated message. In an example, a WTRU may receive signaling about anRLM-RS transmission status (e.g., whether a transmission instance ofRLM-RS was skipped) in a broadcast signaling. The broadcast signalingmay be sent using a SIB or MIB. For example, the WTRU may receive theRLM-RS transmission status in a DCI (e.g. using a RNTI predefined forthe indication of the RLM-RS transmission status). The WTRU may receivethe signaling, for example, in a group common PDCCH. The signaling maybe implicit (e.g., implicitly encoded in a slot format indicator (SFI)).The WTRU may receive the signaling about the RLM-RS transmission statusassociated with a secondary node. The WTRU may receive the signalingabout the RLM-RS transmission status associated with the secondary nodein a dedicated RRC message or broadcast signaling (e.g. SIB). The WTRUmay receive dedicated RRC message or broadcast signaling, for examplefrom a master node. The master node may be in a licensed spectrum.

A WTRU may be configured to determine that a transmission instance ofRLM-RS was skipped based on a characteristic associated with the RLM-RStransmission instance. The WTRU may perform sequence-based detection ofa missing RLM-RS. A WTRU may be configured to determine that atransmission instance of RLM-RS was skipped based on failing to detect acharacteristic associated with the RLM-RS transmission instance (e.g.,during the transmission instance associated with the RLM-RS). Forexample, a WTRU may be configured to determine the status of an RLM-RStransmitted in the past (e.g. at time T-n) implicitly based on acharacteristic associated with the RLM-RS transmission in the future(e.g. at time T).

The characteristic associated with the RLM-RS transmission instance maybe a scrambling ID. The scrambling ID may be associated with an initialvalue of a pseudo-random sequence generator. For example, the WTRU maybe configured with a set (e.g., an ordered set) of N scrambling IDs fora given RLM-RS. A transmission (e.g., each transmission) of the RLM-RSmay be scrambled by selecting one scrambling ID from a preconfigured setof scrambling IDs (e.g., from the ordered set of N scrambling IDs).Selection of the scrambling IDs may be cyclic for subsequenttransmissions (e.g., each subsequent transmission) of the RLM-RS. In anexample, a first transmission of the RLM-RS may be scrambled byselecting a first scrambling ID or may be skipped. A transmissionsubsequent to the first transmission may use the same first scramblingID, e.g., if the first transmission of the RLM-RS is skipped. The firsttransmission of the RLM-RS may be skipped due to LBT failure (e.g., of agNB). The WTRU may determine if and/or how many (e.g. up to N−1) RLM-RStransmission instances were skipped, for example, based on thescrambling ID associated with a transmission instance of the RLM-RS. TheWTRU may calculate the difference between a hypothetical scrambling IDand the actual scrambling ID. For example, a hypothetical scrambling IDmay be a scrambling ID that would have been used if transmission of allthe previous RLM-RS(s) were successful. The cycling of the scrambling IDmay be reset, for example, to further synchronize the scrambling IDusage. The cycling of the scrambling ID may be reset, for example, at apredetermined periodicity (e.g. a cycling periodicity). The cycling ofthe scrambling ID may be reset, for example, by starting from the firstID within the ordered set.

The characteristic associated with the RLM-RS transmission instance maybe resource mapping (e.g., a cyclic shift). For example, the WTRU may beconfigured with a cyclic shift that may be used to determine the timeand/or frequency domain mapping of an RLM-RS (e.g., an RLM-RS sequence).Transmissions (e.g., each transmission) of the RLM-RS may use a specificresource mapping. A subsequent RLM-RS transmission(s) may be shifted intime and/or frequency, for example, using a predefined offset. Forexample, a transmission instance of a RLM-RS may use a first resourcemapping (e.g., based on a first cyclic shift from a starting or areference time/frequency resource). A subsequent transmission instanceof the RLM-RS may use a second resource mapping (e.g., based on a secondcyclic shift). The second resource mapping may be shifted by apredefined offset in time and/or frequency from the first resourcemapping. The second resource mapping may not be shifted by thepredefined offset in time and/or frequency from the first resourcemapping, e.g., if the transmission instance of the RLM-RS is skipped.The WTRU may determine if and/or how many (e.g., up to N−1) RLM-RStransmission instances were skipped, e.g., based on the cyclic shiftassociated with a transmission instance of the RLM-RS. The WTRU maycalculate the difference between a hypothetical cyclic shift and theactual cyclic shift. For example, the hypothetical cyclic shift may be acyclic shift that would have been used if all the previous RLM-RS weresuccessful. Resource mapping may be reset, for example, to furthersynchronize the cyclic shift. Resource mapping may be reset at apredetermined periodicity (e.g. a cycling periodicity). Resource mappingmay be reset to start from a predefined resource mapping.

Proactive compensation may be used to determine a channel status (e.g.,whether a transmission instance of RLM-RS was skipped). A WTRU mayreceive information (e.g., at time T) about the status of one or moretransmission instances of an RLM-RS in the future (e.g., T+n, T+2netc.). In an example, a gNB may be close to exceeding a maximum channeloccupancy time. The gNB may evacuate the channel, for example, to meetregulatory requirements. One or more transmission instances of theRLM-RS may be skipped. The WTRU may learn about an upcoming absence of atransmission(s) of the RLM-RS, for example, based on signaling fromnetwork. The WTRU may be configured to consider what the WTRU learns,for example, as an input. The WTRU may be configured to update an RLMprocess, RLM criteria, and/or set of RLM parameters (e.g., as aproactive compensation) for an upcoming RLM evaluation period.

The WTRU may learn about an upcoming absence of a transmission(s) of theRLM-RS explicitly or implicitly. For example, the signaling about theupcoming absence of the transmission(s) of the RLM-RS may be in a DCI(e.g., with a predefined RNTI). The signaling may be, for example, in agroup common PDCCH. The signaling may be implicitly encoded in an SFI.The information about the upcoming absence of the transmission(s) of theRLM-RS may be signaled in a broadcast message. The information may beprovided implicitly, for example, using a predefined sequence. Thepredefined sequence may indicate the end of a transmission burst. TheWTRU may determine (e.g., derive) the information about the upcomingabsence of the transmission(s) of the RLM-RS based on the starting timeof a gNB transmission burst and/or maximum channel occupancy time. TheWTRU may calculate the starting time of a gNB transmission burst inrelation to detecting a predefined sequence (e.g., in a referencetime/frequency resource). If the WTRU determines (e.g., upondetermining) one or more upcoming RLM-RS is skipped, the WTRU may beconfigured to update an RLM process, RLM criteria, and/or set of RLMparameters (e.g., perform channel status aware RLM as described herein).

Eavesdropping may be used to determine a channel status (e.g., whether atransmission instance of RLM-RS was skipped). A WTRU may determine achannel status based on eavesdropping transmissions, for example, from anon-3GPP air interface. For example, a WiFi capable WTRU connected to a3GPP network may determine the status of a shared spectrum based on WiFitransmissions. One or more transmissions from WiFi may enable the WTRUto determine if the channel may be occupied by non-3GPP interface.Examples of transmissions from WiFi may include Ready to Send(RTS)/Clear to Send (CTS) frames and/or virtual carrier sensing usingNetwork Allocation Vector (NAV). The WTRU may determine how long thetransmissions from WiFi may last. The WTRU may determine whether or notthe transmissions from WiFi may overlap with a potential transmissioninstance of a RLM-RS on the 3GPP interface. The WTRU may use theinformation to update an RLM process, RLM criteria, and/or set of RLMparameters (e.g., perform channel status aware RLM as described herein).

A WTRU may be configured to use signal detection to determine a channelstatus (e.g., whether a transmission instance of RLM-RS was skipped). Inan example, a WTRU may determine the channel status based on detectionof a wake-up signal and/or a preamble signal. The preamble signal mayindicate the beginning of a COT. The WTRU may decode the signal (e.g.,the preamble signal or a wakeup signal) and/or may determine the publicland mobile network (PLMN) and/or the physical cell identity (PCI) ofthe transmitter. The WTRU may determine whether the signal indicatesthat the WTRU's serving or neighboring cell has occupied the channel,for example, based on the PLMN and/or the PCI. If the signal contains anindication of a COT structure (e.g., SFI), the WTRU may determine thechannel status for the indicated period of time. The WTRU may determinethe channel status of an (e.g., each) sub-band within a DL BWPseparately.

An RLM process, RLM criteria, and/or set of RLM parameters may beupdated to process, handle, and/or react to an ambiguous channel. A WTRUmay be configured to monitor downlink quality based on RLM-RSmeasurement samples over a predefined time period, for example, as apart of RLM. The predefined time period may correspond to an evaluationperiod. The evaluation period may be a function of one or more of thefollowing: type of RLM-RS(s), periodicity of the RLM-RS(s), type ofindication(s) (e.g., an IS or OOS indication(s)), DRX configuration, orthe like. The WTRU may be configured to compare an estimated downlinkquality against thresholds (e.g., Qin and/or Qout). The WTRU may beconfigured to generate an IS/OOS indication based on the comparison. TheWTRU may be configured to send an IS/OOS indication to higher layers(e.g., RRC). A higher layer filter (e.g., layer 3 filter) may be appliedto the IS/OOS indications. The higher layer filter may havepreconfigured coefficients. Two successive indications from lowerlayer(s) may be separated, for example, by at least a time interval. Thetime interval may be predefined. The time interval may correspond to anindication interval. The indication interval may be a function of one ormore of the following: type of RLM-RS(s), periodicity of the RLM-RS(s),type of indication(s) (an IS or OOS indication(s)), DRX configuration,or the like.

Measurement samples may be selected and/or scaled, for example, as afunction of channel status. A WTRU may be configured to receiveRLM-RS(s) within a time window configured using, for example, RLM-RSMeasurement Timing Configuration (RMTC). Being configured to receiveRLM-RS(s) within a time window may account for timing uncertainty (e.g.,due to LBT). The RMTC may correspond to SS Block based MeasurementTiming Configuration (SMTC), for example, if SSB is used as RLM-RS. TheRMTC configuration may include one or more of periodicity, offset, andduration. The RMTC configuration may be expressed as a number ofsubframes. For example, the WTRU may expect RLM-RS in any symbol withinthe time window (e.g., defined by the RMTC).

Measurement samples may be selected and/or scaled during an evaluationperiod. A WTRU may be configured with an evaluation period. Theevaluation period may be a multiple of RLM-RS periodicity or theperiodicity of RMTC (e.g., in case of RMTC). The RLM-RS may betransmitted multiple times, for example, within the evaluation period.The measurement samples within the evaluation period may fluctuate dueto, for example, channel ambiguity. The fluctuation may be rapid. TheWTRU may be configured to derive channel quality based on, for example,at least n number of measurement samples that are unambiguous. The valueof n may be configured, e.g., preconfigured to be a function of at leastRLM-RS periodicity, type of indication IS/OOS, DRX configuration, or thelike.

A WTRU may be configured to adjust and/or scale higher layercoefficients, for example, based on a channel status determination. Forexample, the WTRU may apply less weight for measurement samplescollected when the channel state is ambiguous. The WTRU may adjust thehigher layer coefficients based on the nature of interference. Forexample, different weights may be used for 3GPP vs. non-3GPPinterference. Different weights may be used for coordinated vs.uncoordinated interference. The WTRU may be configured to determine theprobability of detecting a (e.g., each) RLM-RS sample(s) within theevaluation period. The WTRU may adjust the weight of a layer 3 filterbased on the probability of detecting the RLM-RS sample(s).

A WTRU may be configured to select a preconfigured number of measurementsamples, for example, from a group of measurement samples. The WTRU maydisregard samples which are outliers, for example, based on, apreconfigured offset if the WTRU is configured to select a preconfigurednumber of measurement samples from a group of measurement samples. Theoffset (e.g., preconfigured) may be BWP specific and/or may be receivedin a BWP configuration. The number of measurement samples (e.g.,preconfigured) may be BWP specific and/or may be received in a BWPconfiguration.

Channel quality may be determined by using a fallback to predefineddownlink signals. A WTRU may be configured to use one or more predefineddownlink signals for RLM, for example, when an RLM-RS is not detectedwithin an RMTC window. A WTRU may be configured to use one or morepredefined downlink signals for RLM, for example, when more than apreconfigured number of measurement samples are ambiguous within anevaluation period. The WTRU may determine channel quality based on aRS(s) that is not explicitly configured for RLM. For example, the RS(s)may include a beam management RS, CSI-RS configured for CSI reporting,and/or SSB if only CSI-RS is configured for RLM. The RS may bequasi-collocated (QCLed) with at least one preconfigured RLM-RS. TheWTRU may determine the channel quality based on a successful receptionof DCI related to a broadcast transmission (e.g. SI-RNTI in a commonsearch space). For example, the WTRU may generate an IS indication if apreconfigured number of DCIs are successfully decoded within a timeperiod. The time period may include an indication interval or evaluationinterval. An OOS indication may be generated if a preconfigured numberof DCIs are not successfully decoded within the time period. The WTRUmay monitor for an RLM-RS(s) and/or predefined downlink signals withinthe RMTC window. The WTRU may monitor for the RLM-RS(s) within the RMTCwindow and fallback to monitoring predefined downlink signals outsidethe RMTC window. The WTRU may monitor the predefined downlink signalsoutside the RMTC window until the next RMTC window or a condition togenerate an IS/OOS indication(s) is satisfied (e.g., whichever isearlier).

A WTRU may be configured with a plurality (e.g., X number) of RLM-RSsfor RLM. An RLM-RS (e.g. each RLM-RS) may be associated with atransmission beam. The WTRU may determine whether to generate IS, OOS,or NS based on, for example, a channel status in the plurality ofRLM-RS(s). For example, if more than n RLM-RS results are ambiguous, theWTRU may be configured to generate an NS(s). If the number of RLM-RSwith ambiguous results is more than a number of RLM-RS with an OOS(s),the WTRU may generate an NS(s).

The WTRU may be configured to select n RLM-RS(s) out of X configuredRLM-RSs for an RLM evaluation, based on, for example, the channel status(e.g., determination of whether a RLM-RS is skipped or not) associatedwith the RLM-RS(s). For example, the WTRU may be configured to performan RLM evaluation based on a CSI-RS resource QCLed with SSB, forexample, when the WTRU determines that the SSB transmission is skipped(e.g., due to LBT).

A block error rate (BLER) may be determined during an ambiguous channel.A WTRU may be configured to determine the BLER during an ambiguouschannel condition based on, for example, a previous BLER value(s)associated with the channel. For example, the WTRU may compute (e.g.,calculate) the BLER based on a weighted average of the previous n BLERvalues of the channel. The WTRU may add a preconfigured negative offsetto the averaged BLER value. For example, the negative offset may beincremented during indication intervals (e.g., each indicationinterval). The incrementation of the negative offset may be additiveincrease and/or multiplicative increase. The negative offset may be afunction of, for example, one or more of a number of unambiguousmeasurement samples collected during an evaluation period, an RLM-RSmeasurement result, one or more channel measurements (e.g., a level ofinterference), a number of missed transmission opportunities, one ormore sources of interference (e.g. different values for 3GPP vs non-3GPPinterference), or the like. The negative offset may be reset to aninitial value when an IS indication is received. The WTRU may beconfigured to generate an IS/OOS/NS indication(s) based on, for example,comparing the computed BLER value with the Qin/Qout threshold.

An indication associated with an ambiguous channel (e.g., a No-Sync(NS)) may be generated. A WTRU may be configured to generate anindication (e.g., NS indication) that is different from an IS and OOSindication(s). The WTRU may be configured to generate the indication toinform higher layers of an ambiguous channel condition (e.g., during anRLM process). For example, an NS indication may be generated when thechannel status is determined to be ambiguous using one or more examplesdescribed herein (e.g., when an RLM-RS is determined not to bereceived). The NS indication may be generated when lower layers may notconclusively determine the channel quality, for example, due to theabsence of RLM-RS transmission(s). The NS indication may be generatedwhen lower layers may not conclusively determine the channel quality,e.g. due to the masking of RLM-RS in a busy channel.

The WTRU may be configured to track a number of NS indications that theWTRU received from lower layers. For example, the WTRU may maintain anNS counter of a number of (e.g., consecutive) NS indications. The NScounter may include N312 or NS310. The WTRU may be configured to resetthe NS counter, for example, upon receiving an IS indication. The WTRUmay be configured not to reset the NS counter, for example, uponreceiving an OOS indication. The WTRU may be configured to perform apredefined action, for example, when the NS counter reaches apreconfigured maximum value. Consecutive NS indications may indicatethat the channel has been busy for a period (e.g., relatively longperiod) of time. For example, the channel may have been busy for aperiod of time due to a relatively high density of competing nodesand/or relatively high channel load that results in failedtransmissions. The WTRU may start a timer (e.g., T310) if the timer isnot already running. The WTRU may trigger an RLF when a timer (e.g.,T310) is running and the NS counter reaches a maximum value. The WTRUmay start a timer (e.g., T310) when the sum of the OOS counter and theNS counter reaches a maximum value. The WTRU may exclude the timeinterval from a timer when an NS indication is received. For example,the WTRU may exclude the time interval from T310 when an NS indicationis received, when T310 is running. The WTRU may pause the timer (e.g.,T310) when an NS indication is received. The WTRU may interpret an NSindication based on the status of the timer (e.g., T310). For example,the WTRU may treat an NS indication as an IS indication when T310 isrunning. The WTRU may treat an NS indication as an OOS indication whenT310 is not running.

The WTRU may be configured to interpret an NS indication differentlybased on previous indications. In examples, the WTRU may be configuredto interpret the NS indication based on, for example, previousindications from the lower layers. For example, if the number of OOSindications out of ‘n’ previous indications from lower layers is above anumber (e.g., preconfigured number), the WTRU may interpret the NSindication as an OOS indication. If the number of IS indications out of‘n’ previous indications from lower layers is above a number (e.g.,preconfigured number), the WTRU may interpret the NS indication as an ISindication. If the number of NS indications out of ‘n’ previousindications from lower layers is above a number (e.g., preconfigurednumber), the WTRU may start a timer. If an IS/OOS indication is notreceived before the expiration of the timer, the WTRU may be configuredto either start T310 timer or trigger RLF (e.g., if T310 is alreadyrunning).

A counter (e.g., an OOS counter) may be incremented by a fractionalvalue. For example, a WTRU may be configured to increment an OOS counterby a fractional value (e.g., increment less than 1) during an ambiguouschannel condition. The WTRU may be configured (e.g., preconfigured) witha fractional value. The WTRU may receive a fractional value in an RRCsignal or via system information broadcast. The WTRU may determine thefractional value based on, for example, one or more of an RLM-RSmeasurement result, one or more channel measurements (e.g., level ofinterference), a number of missed transmission opportunities, a sourceof interference (e.g. different values for 3GPP vs non-3GPPinterference), or the like. The WTRU may be configured to use afractional increment (e.g., increment an OOS counter by a fractionalvalue) when an NS indication is received. The WTRU may be configured touse a fractional increment (e.g., increment an OOS counter by afractional value) when an OOS indication is received and the channelstatus is determined to be ambiguous (e.g., using one or more examplesdescribed herein).

A WTRU may be configured to use zero power resources for RLM (e.g.,evaluation). For example, a zero power resource may be a time/frequencyresource on which the network node does not transmit a signal (e.g., isblanked). A CSI-IM (e.g., that may also be referred to as an RLM-IM) maybe an example of a zero power resource. A WTRU may be configured withRLM channel state information interference management (CSI-IM) resourcesin a DL BWP, for example in addition to an RLM-RS(s), for RLM. The WTRUmay be configured with RLM CSI-IM resources in a (e.g., each) DL BWP.The WTRU may monitor the CSI-IM resources in an active DL BWP. The WTRUmay evaluate the level of interference experienced in the active DL BWPbased on the monitoring of the CSI-IM resources. The CSI-IM resourcesmay be configured on the same resources (e.g., RBs) as the RLM-RS(s).The WTRU may perform L1 measurements on ZP and/or non-ZP resources. TheWTRU may keep a counter for different types (e.g., each type) ofresources. For example, the WTRU may keep a counter for each of the ZPresource(s) and of the non-ZP resource(s).

In an example, the WTRU may generate and/or send (e.g., to higherlayers) an indication based on the evaluation of the interference levelon CSI-IM resources. The WTRU may send the indication in addition to anIS indication(s) and an OOS indication(s). For example, the indicationmay be an unknown sync (US) indication. The higher layers may restart anRLF timer if the higher layers receive multiple (e.g., upon reception ofN) US indications. The WTRU may be configured with a thresholdassociated with the US indication (e.g., an US-specific counterthreshold). The WTRU may declare RLF if the threshold is reached (e.g.,upon reaching the US-specific counter threshold).

In an example, the WTRU may indicate IS and/or OOS indications to higherlayers. For example, the WTRU may only send a legacy IS-OOS (e.g., maynot use the US indication). The OOS indication may be generated and/orsent based on (e.g., subject to) the measurement results on CSI-IMresources. The WTRU may be configured to refrain from sending an OOSindication if a measurement result(s) on CSI-IM resources is above athreshold. In examples, the CSI-IM measurement being above a thresholdmay indicate a LBT failure and/or may not indicate poor channelconditions. The WTRU may send the IS, skip the indication, and/ortransmit an NS indication. As an example, the WTRU may send the IS, skipthe indication, and/or transmit a non-sync indication without takinginto account the CSI-IM measurement result. For example, the WTRU maysend the IS, skip the indication, and/or transmit an NS indicationwithout taking into account the CSI-IM measurement result if themeasurement of the RLM-RS meets the criteria for IS, skipping theindication, and/or transmitting an NS indication. In an example, the OOSindication may be conditioned on a CSI-IM measurement. Whether to sendIS, skip the indication, and/or transmit an NS indication may not beconditioned on a CSI-IM measurement.

A WTRU may be configured to receive a configuration of RLM-RS persub-band (e.g., for a configured DL BWP). For example, a configurationof RLM-RS per sub-band may be received for each configured DL BWP. TheWTRU may determine which RLM-RS to monitor for RLM, for example, basedon RSSI and/or channel occupancy (CO) measurements on a correspondingsub-band (e.g., a sub-band that corresponds to a received configurationof RLM-RS(s)). For example, if an RSSI or CO measurement result in agiven sub-band of an active DL BWP is higher than a configuredthreshold, the WTRU may not consider the configured RLM-RS resourceswithin the sub-band for RLM. The WTRU may perform RLM evaluation onlow-loaded sub-bands. The RSSI or CO measurement result may be lowerthan the configured threshold on low-loaded sub-bands. The WTRU may beconfigured to refrain from performing RLM on sub-bands that areindicated as busy or loaded, for example, based on the RSSI or COmeasurement result.

In an example, if the contention metric in one or more sub-bands in anactive DL BWP is higher than a threshold, the WTRU may activatepre-configured RLM-RS resources in other sub-bands of the active DL BWP.For example, the WTRU may activate the pre-configured RLM-RS resourceswhen the contention metric in each of the sub-bands currently beingmeasured is higher than a threshold.

In an example, the WTRU may maintain multiple RLM loops. As used herein,a loop may refer to an RLM process (e.g., an independent RLM process)with one or more associated RLM resources, Qin-Qout thresholds, timersand/or counters. For example, the WTRU may maintain one RLM loop persub-band. The WTRU may trigger RLF when one or more sub-bands of theactive DL BWP reach an RLF criteria (e.g., N OOS indications in eachsub-band). For example, an RLF may be triggered when all sub-bands ofthe active DL BWP reach the RLF criteria.

A WTRU may be configured to use aperiodic or semi-persistent CSI-RSresources for RLM. Aperiodic or semi-persistent CSI-RS transmissions maybe used for RLM to deal with the uncertainty of periodic CSI-RStransmissions due to LBT. Periodic CSI-RS transmissions may beuncertain, for example, due to LBT. The uncertainty may be dealt with,for example, using aperiodic or semi-persistent CSI-RS transmissions forRLM. The WTRU may be pre-configured with multiple CSI-RS resources, forexample, in different sub-bands. The WTRU may expect to receive a MAC CEor DCI. The WTRU may activate/deactivate a set of CSI-RS(s) based on anLBT result in the corresponding sub-band of the active DL BWP and/or thereceived MAC CE or DCI. For example, the WTRU may use one or moreaperiodic or semi-persistent CSI-RS resources for RLM when the channelload on the active DL BWP exceeds a certain level (e.g., indicating thatthe configured periodic RLM-RS(s) is uncertain). If the WTRU does notreceive a MAC CE or DCI (e.g., due to bad channel conditions) within atime window (e.g., a preconfigured time window), the WTRU may send an OSindication to higher layers for the time window. The preconfigured timewindow may be, for example, an RLM evaluation period.

The WTRU may receive a DCI for an aperiodic CSI-RS transmission(s)(e.g., when the channel is acquired by the gNB). The WTRU may receive anindication that the WTRU may perform RLM on indicated RSs (e.g., theaperiodic CSI-RS transmission(s)). The WTRU may receive the indicationin the DCI. The DCI may be WTRU-specific or common to multiple WTRUsconfigured with a DL BWP containing the transmitted aperiodic CSI-RSresource. For example, the DL BWP may be an active DL BWP.

A WTRU may be configured to perform channel status aware RLM based on astatus of a timer, (e.g., T310). A WTRU may be configured to perform oneor more of the examples described herein, for example, as a function ofthe status of a timer related to RLF (e.g., T310). For example, the WTRUmay be configured to perform legacy RLM when T310 is not running. TheWTRU may switch to channel status aware RLM when T310 is running. TheWTRU may determine an increment value for an IS counter, for example,based on the status of timer T310. In an example, a first incrementvalue may be used when T310 is running (e.g., less than 1), and a secondincrement value may be used when T310 is not running (e.g., 1).

A WTRU may be configured to perform autonomous UL triggering of a signalrelated to RLM and/or RLM-RS reception in a portion of a UL grant thatis relinquished by a WTRU. A WTRU may be configured to relinquish awhole or parts of a UL grant, based on, for example, a status of anRLM-RS transmission in the past. The UL grant may be dynamically orsemi-statically configured for the WTRU. The WTRU may autonomouslyacquire the channel, for example, after a full LBT. For example, theWTRU may have failed to receive one or more RLM-RS(s) in a previous timeperiod. The WTRU RLM counter (e.g., N310 or NS counter) may reach acondition (e.g., a critical condition including a preconfigured criticalcondition). The WTRU RLM timer (e.g. T310) may reach a condition (e.g.,a critical condition including a preconfigured critical condition). Uponone or more of triggers (e.g., as described herein), the WTRU maytransmit an indication in the UL indicating that RLM-RS was not receivedreliably in a previous time period, and/or may relinquish the UL grant.The triggers may include the WTRU's failure to receive one or moreRLM-RS(s) in a previous time period, or that the WTRU RLM counter or RLMtimer reaches a condition (e.g., a critical condition). The network mayuse the channel to transmit an RLM-RS(s) and/or a signal similar to anRLM-RS(s). The WTRU may be configured to monitor for an RLM-RS signal inthe remaining portion of the UL grant. The WTRU may indicate to thenetwork the portion of the transmission opportunity where the RLM-RS maybe transmitted. For example, the WTRU may transmit an autonomous uplink(AUL)-UCI to indicate to the network the portion of the transmissionopportunity. The WTRU may transmit a bitmap of most recently receivedRLM-RS (e.g., in an AUL).

A WTRU may be configured to adapt one or more counters and/or timers,for example, based on channel occupancy. The counters and/or timers maybe used as part of an RLM process. A WTRU (e.g., that is performing RLM)may apply a set of counters and timers based on current, past, and/orobserved channel occupancy. The timers (e.g., N310, N311, and/or T310)may depend on current, past, and/or observed channel occupancy. Forexample, RLM parameters may be set such that T310 has a longer durationfor higher channel occupancy and a lower duration for lower channeloccupancy. Using a different set of RLM parameters and/or a differentRLM process may be use to avoid premature declaration of RLF (e.g., dueto failure of a network to provide an RLM-RS under high channel load).

Higher layers (e.g., RRC) may configure one or more RLM parameter(s)with more than one value. An RLM parameter may include at least one ofthe N310 and N311 counters and the T310 timer. For example, T310 may beconfigured with two possible values. A WTRU may determine the applicablevalue of the one or more RLM parameter(s) based on a metric or anindication (for example, as described herein). The WTRU may (e.g., basedon the indication) multiply a value of an RLM parameter by a factor. Forexample, the WTRU may double the length of the T310 timer by applying afactor of 2 to the T310 timer. The factor may be pre-defined and/orconfigured. For example, a multiplicative factor may be applied upondetermining that the channel is considered busy or occupied.

A metric may be determined (e.g., defined). The metric may correspond toan estimation and/or a measurement of the channel occupancy. Forexample, a channel occupancy metric including a percentage of samplesfor which RSSI is above a threshold may be used. The WTRU may beconfigured with at least one threshold for the metric. The WTRU mayapply the value of the one or more RLM parameter(s) as a function of thevalue of the metric compared to the at least one threshold. For example,a single channel occupancy threshold may be configured, for example,along with two values of T310. The WTRU may apply a first value if thechannel occupancy is below the threshold and a second value if thechannel occupancy is above the threshold. The at least one threshold maybe pre-defined or configured by higher layers. The at least onethreshold may be the same as the threshold used for triggering ameasurement report of the channel occupancy.

A WTRU may determine the applicable value of the one or more RLMparameter(s) based on a dynamic indication from the network. Theindication may be received via a MAC CE. The indication may be receivedvia PDCCH that is received from a common search space or WTRU-specificsearch space. For example, the indication may be provided in a commonDCI (e.g., the same DCI that contains SFI). The indication may beprovided in a DCI (e.g., the same DCI) that contains a presenceindication. The indication may be provided in a separate DCI. Theinformation may include (e.g., consist of) an index to the applicablevalue. The information may include a channel occupancy measurement(e.g., taken by the network). The WTRU may determine the applicablevalue based on one or more of the indicated channel occupancy (fromPDCCH), the measured channel occupancy, or at least one threshold. As anexample, the WTRU may determine the applicable value based on theindicated channel occupancy (e.g., from PDCCH) and at least onethreshold. The WTRU may determine the applicable value based on themeasured channel occupancy and at least one threshold. For example, theWTRU may determine the applicable value based on whether the maximum ofthe two channel occupancies (e.g., the indicated channel occupancy andthe measured channel occupancy) is above a threshold.

The WTRU may determine the applicable value of the one or more RLMparameter(s) based on a property of RLM-RS. For example, the property ofRLM-RS may include a scrambling ID. The WTRU may attempt to detect anRLM-RS using at least one property. The WTRU may determine the value ofthe at least one property based on the highest likelihood (e.g., thehighest correlation). For example, the WTRU may apply a first value ofT310 if an RLM-RS is detected with a first scrambling ID. The WTRU mayapply a second value of T310 if the RLM-RS is detected with a secondscrambling ID. The values for the at least one property may beconfigured, for example, by higher layers.

The WTRU may be configured with two or more RLM-RS resources. Theresources (e.g., each resource) may be associated with respective valuesof the RLM parameters. The WTRU may perform RLM independently on aRLM-RS resource(s) (e.g., each RLM-RS resource). The WTRU may declareRLF when the T310 timer has expired for RLM-RS resources, and thechannel quality has not recovered since T310 has last expired forresources. For example, the WTRU may declare RLF only when the T310timer has expired for all RLM-RS resources, and the channel quality hasnot recovered since T310 has last expired for resources (e.g., eachresource). The WTRU may determine that the channel quality has notrecovered based on receiving at least one N311 in-sync indication(s).The network may select the RLM-RS resource, for example, as a functionof a channel occupancy. The network may select the RLM-RS resource, forexample, as a function of how frequently the RLM-RS is transmitted dueto failure of accessing the channel.

The WTRU may start monitoring for a second RLM-RS resource, for example,when T310 is running for a first RLM-RS resource. For example, the WTRUmay start monitoring for the second RLM-RS resource only when T310 isrunning for the first RLM-RS resource. The first RLM-RS and the secondRLM-RS may be configured with different periodicities. If the firstRLM-RS and the second RLM-RS are configured with differentperiodicities, the WTRU may monitor the RLM-RS configured with a lowperiod when (e.g., only if) problems are occurring with the RLM-RSconfigured with a high period. For example, the WTRU may monitor theRLM-RS configured with a low period if the WTRU fails to detect theRLM-RS configured with a high period above a quality threshold. Thisapproach may be more battery-efficient. For example, the WTRU maymonitor the RLM-RS configured with a low period only when a channelbecomes busy. One or more high period RLM-RS resources may be dropped(e.g., due to LBT failure) when a channel becomes busy.

A WTRU may be configured to declare RLF if a channel the WTRU is usingis busy, for example, for an extended period. As an example, the WTRUmay declare RLF if the WTRU fails to acquire the channel for uplinkafter a given amount of time. The WTRU may declare RLF if the WTRU failsto acquire the channel for uplink after a number of attempts to acquirethe channel have failed (e.g., a number of LBTs have failed). The WTRUmay transmit in an unlicensed channel. The WTRU may be configured toverify that the channel is idle (e.g., for at least a sensing interval)before the WTRU transmits. LBT failure may include a situation where achannel is assessed to be not idle (e.g., based on an energy detection).For example, a LBT failure may correspond to a situation where a channelis assessed to be not idle for at least a determined time interval priorto a transmission.

A WTRU may be configured to declare RLF based on LBT failures (e.g., toomany LBT failures). The WTRU may be configured to monitor channelavailability for UL transmissions in a connected state. The WTRU may beconfigured to declare RLF based on triggers (e.g., triggers associatedwith channel availability). For example, the WTRU may be configured todeclare RLF if the channel cannot be acquired for an UL transmission fora predefined time. The WTRU may be configured to declare RLF if thechannel cannot be acquired for UL transmission for a number of attempts(e.g., due to LBT failure). The WTRU may avoid being stuck in a good butbusy channel (e.g., using the approaches herein).

The WTRU may be configured to defer a transmission to a future time whenthe channel is free, for example, upon LBT failure. The WTRU may beconfigured to keep count of LBT failure occurrences that lead todeferred transmissions. As used herein, the terms LBT failure counter,skipped transmission counter, deferred transmission counter,transmission attempt counter may be used interchangeably. In an example,the WTRU may be configured to maintain a common LBT failure counteracross one or more UL channels. For example, the common LBT failurecounter may be maintained across all UL channels. The UL channels mayinclude, for example, physical random access channel (PRACH), PUCCHand/or PUSCH. In an example, the WTRU may be configured to maintain afailed LBT counter, e.g., specific to the UL channel associated with thetransmission. For example, the WTRU may maintain separate counters forone or more of PRACH, PUCCH and PUSCH channels. The WTRU may beconfigured to declare RLF when a maximum value (e.g.,preconfigured/predefined) for at least one of the LBT failure countersis reached. The WTRU may be configured to declare RLF, for example,based on a sum of two or more counters reaching a maximum value.

A trigger related to RLF may be generated based on deferred preambletransmissions. A WTRU may trigger RLF based on deferred preambletransmissions (e.g., too many deferred preamble transmissions). A WTRUmay be configured to determine (e.g., ensure) a success of LBT, forexample, before the WTRU makes a preamble transmission. For example, theWTRU may use a counter keep count of a number of preamble transmissionsthat are deferred or skipped due to a failed LBT(s). The counter may bedifferent from a preamble transmission counter or a power rampingcounter (e.g. a skipped preamble transmission counter). The counter maybe a skipped preamble transmission counter. The WTRU may be configuredto increment the skipped preamble transmission counter if a preambletransmission is canceled upon LBT failure. The WTRU may be configured totrigger RLF if the skipped preamble transmission counter reaches a value(e.g., preconfigured value). The WTRU may reset the skipped preambletransmission counter if a random access response (RAR) is received(e.g., successfully). The WTRU may be configured to trigger RLF if thesum of the skipped preamble transmission counter and the preambletransmission counter is above a value (e.g., preconfigured value). TheWTRU may be configured to increment the preamble transmission counter bya fractional value if a preamble transmission is skipped due to LBTfailure. The fractional value may be less than one. The fractional valuemay be configured, for example, via RRC signaling or in systeminformation broadcast.

The WTRU may trigger RLF, for example, upon expiration of a timer (e.g.a skipped preamble timer). The WTRU may be configured to start the timerwhen a preamble transmission is deferred, e.g., due to an LBT failure.The WTRU may stop the timer if lower layers indicate that the preambleis transmitted.

An indication about an LBT outcome and/or a status of a transmission maybe defined and/or sent from lower layers to MAC (e.g., a MAC layer). Asan example, the MAC layer may be used to increment the skipped preamblecounter and/or may start a skipped preamble timer, for example, uponreceiving an indication informing of a transmission failure due to LBT.

A trigger related to RLF may be generated based on deferred ULtransmissions (e.g., too many deferred UL transmissions). A WTRU may beconfigured to determine (e.g., ensure) successful LBT, for example,before the WTRU makes a PUSCH and/or PUCCH transmission(s). The WTRU mayperform LBT in a cell (e.g., operating in an unlicensed spectrum). TheWTRU may determine to defer and/or skip an UL transmission, for example,based on a determination of a failed LBT. The WTRU may determine thatthe number of deferred UL transmissions exceeds a threshold. The WTRUmay send an indication of RLF based on the determination that the numberof the deferred UL transmissions exceeds the threshold. The WTRU maydetermine that UL access latency exceeds a threshold. The WTRU may sendan indication of RLF based on the determination that the UL accesslatency exceeds the threshold. The uplink transmission may include MSG3transmission or any other UL-SCH transmission. Examples for a skippedpreamble transmission(s) (e.g., as described herein) may be applied fora skipped PUSCH and/or deferred PUCCH transmission(s). Counters and/ortimers may be separate for PUCCH and PUSCH. The threshold may beassociated with (e.g., specific to) an UL channel. The WTRU may beconfigured to maintain a counter for the deferred UI transmissions.

The WTRU may be configured to determine a fractional increment to an OOScounter as a function of a number of transmissions. The WTRU may beconfigured to determine a fractional increment to an OOS counter as afunction of a number of skipped preamble transmissions. The WTRU may beconfigured to determine a fractional increment to an OOS counter as afunction of a number of skipped PUSCH transmissions. The WTRU may beconfigured to determine a fractional increment to an OOS counter as afunction of a number of skipped PUCCH transmissions. The WTRU mayinterpret an NS indication as an OOS indication if the number of skippedtransmissions is above a threshold. The WTRU may interpret an NSindication as an OOS indication if the number of skipped preambletransmissions is above a threshold. The WTRU may interpret an NSindication as an OOS indication if the number of skipped PUSCHtransmissions is above a threshold. The WTRU may interpret an NSindication as an OOS indication if the number of skipped PUCCHtransmissions is above a threshold.

A WTRU may be configured to maintain a deferred UL transmission counter(e.g., an LBT failure counter). In examples, WTRU transmission occasionsmay be frequent or may occur close to each other. Incrementing the LBTfailure counter upon every LBT failure may result in an earlydeclaration of RLF, for example, if a common counter is configured formultiple UL channels. A WTRU may fractionally increment the LBT failurecounter upon an LBT failure, and/or n LBT failures may result inincrement of the counter. For example, the WTRU may fractionallyincrement the LBT failure counter upon each LBT failure. In examples,the WTRU may increment the LBT failure counter (e.g., once) upon nconsecutive LBT failures. The n consecutive LBT failures may have no LBTsuccess in between. The WTRU may be configured to refrain fromincrementing the LBT failure counter if n consecutive LBT failures donot occur. The increment of the counter may correspond (e.g., bespecific) to an UL channel.

The WTRU may be configured to increment an LBT failure counter as afunction of a given UL channel. The WTRU may be configured to maintain acommon counter for LBT failure during a UL transmission. For example,the common counter may be used for LBT failure during any ULtransmission and/or for transmissions on any UL channel. The incrementsto the counter may be a function of a specific UL channel (e.g.,specific properties or characteristics of a UL channel). As an example,the WTRU may be configured to increment the counter based on theperiodicity of transmission occasions associated with a UL channel. Forexample, smaller increments may be added when LBT failure occurs duringfrequently occurring UL channels. Larger increments may be added whenLBT failure occurs during less frequently occurring UL channels. Theincrements may be preconfigured (e.g., in a system information broadcastor RRC configuration). The WTRU may determine the increments, forexample, based on a periodicity of transmission occasions associatedwith the UL channel.

A WTRU may be configured to implement rules to control when an LBTfailure counter is incremented. For example, one or more timers may beused to determine whether the LBT failure counter is to be incrementedbased on an observed or detected criteria(ion). Using the one or moretimers may avoid frequent increments to the LBT failure counter. In anexample, the WTRU may be configured to increment the LBT failure counterat most once within a time interval. The WTRU may start a timer when theLBT failure counter is incremented. The WTRU may not increment the LBTfailure counter during subsequent LBT failures if the timer is running.If the timer is not running or is expired and an LBT failure occurs, theWTRU may increment the LBT failure counter and/or start the timer again.

The WTRU may be configured to increment the LBT failure counter if n ormore LBT failures occur within a time interval. For example, the WTRUmay increment the LBT failure counter if n or more consecutive LBTfailures are observed within a time interval.

The duration of a timer and/or the value of n may be configured by thesystem information broadcast or RRC configuration. In examples, the WTRUmay be configured to determine the value of n and/or the timer based ona quality of service and/or a logical channel that triggered the ULtransmission.

A WTRU may be configured to reset the LBT failure counter based on acertain criteria(ion). The WTRU may be configured to reset the LBTfailure counter if the WTRU determines that the channel is available fortransmission. For example, the WTRU may reset the LBT failure counter ifCCA is successful. The WTRU may reset the LBT failure counter if a ULtransmission is performed. The UL transmission may be, for example, apreamble, PUCCH or PUSCH transmission. The WTRU may reset the counter ifN number of CCA successes are detected and/or N number of ULtransmissions are performed. For example, the WTRU may be configured torefrain from resetting the counter when N CCA successes are not detectedand/or N UL transmissions are not performed. The WTRU may stop the timerrelated to LBT failure counting if the counter is reset.

The WTRU may be configured to reset the LBT failure counter if aresponse to a preamble transmission (e.g., an RAR) is received.

A WTRU may be configured with a RLM behavior as a function of LBTfailures. In examples, the function related to counting LBT failuresand/or impacting the WTRU behavior based on LBT failures may be modeledas RLM (e.g., RLM process).

The WTRU may trigger RLF when the LBT counter value reaches a threshold(e.g., preconfigured maximum value). The WTRU may trigger RLF based on acombination of the LBT failure counter and the status of an RLM process(e.g., based on IS/OOS indications). For example, the WTRU may triggerRLF based on a maximum number of LBT failures when a timer related toRLM is running. The timer may be, for example, T310. For example, theWTRU may be configured to refrain from triggering RLF based on themaximum number of LBT failures when the timer related to RLM is notrunning.

In an example, when the LBT failure counter reaches a preconfiguredvalue, the WTRU may start a timer. When a successful transmission (e.g.,a preamble transmission and/or any other UL transmission) cannot beperformed within the timer expiry, the WTRU may trigger RLF. One or morestates of an RLM behavior may be configured for the WTRU. For example,the WTRU may be configured with two states of an RLM behavior. In afirst state, the WTRU may monitor the status of the channel. If the LBTcounter indicates that the channel is busy, the WTRU may enter a secondstate. In the second state (e.g., modeled as a recovery stage) the WTRUmay attempt a successful transmission within a time period. If no ULtransmissions are performed within the expiry of a timer, the WTRU maydeclare RLF.

A WTRU may be configured to perform BWP failure detection and/orrecovery using autonomous BWP switching. A WTRU may be configured toperform LBT at the granularity of a BWP(s). Different BWPs associatedwith a serving cell may have varying channel status, load(s), orinterferences. The WTRU may be configured to perform RLM based on theRLM-RS(s) confined to an active BWP. The WTRU may be configured todeclare a BWP failure when an RLF is detected in the active BWP, forexample based on one or more RLF triggers described herein. For example,a BWP failure may be declared when more than n RLM-RS resources have notbeen transmitted (e.g., for more than x indication periods). The WTRUmay be configured to autonomously switch to a different BWP belonging tothe same serving cell, e.g. when an RLF is detected in the active BWP. AWTRU may switch to a BWP that is chosen from a plurality of BWPs (e.g.,preconfigured BWPs) for a WTRU. The WTRU may select the BWP based on thequality of the BWP(s) (e.g. based on SSB and/or CSI-RS measurement). TheWTRU may select the BWP that has the earliest channel availability. TheWTRU may select the BWP that has a low channel load and/or channeloccupancy (e.g. based on RSSI and/or ZP-RS measurement). The WTRU mayselect the default BWP or fallback BWP (e.g., that is specificallypreconfigured for the WTRU). The WTRU may indicate the autonomous BWPswitch to the network, for example, using an RA process including aselection of a preamble that belongs to the BWP that the WTRU isswitching to. The WTRU may indicate the reason for the autonomous BWPswitch (e.g., channel busy for a predefined time or RSSI result).

A WTRU may be configured to take a corrective action when the WTRUreceives an indication that the channel load is above a threshold. Thecorrective action may include, for example, at least one of declaringRLF or applying a stored configuration for handover (e.g., a conditionalhandover). The indication may include, for example, detecting that aconfigured RS is above a threshold or decoding DCI indicating a highload condition. The WTRU may apply the corrective action if the WTRU hasfailed to detect a RS (e.g. RLM-RS) above a threshold, or if T310 isrunning or has expired.

A channel status may be reported. A network may configure RLM-RSresources for a WTRU. A WTRU may be configured to report a BWP specificRSSI measurement for an active BWP and one or more configured BWP(s). AWTRU may be configured to report a BWP specific ZP-RS measurement for anactive BWP and one or more configured BWP(s). The WTRU may be configuredto trigger the report based on, for example, expiration of a periodictimer and/or based on a request from the network. The report may beconfigured as an event triggered report. The events may include, forexample, an active BWP RSSI being above or below a threshold, an activeBWP RSSI being above or below the RSSI of a configured BWP, a number ofNS indications in an active BWP being above a threshold, or a number ofskipped RLM-RS transmissions being above a threshold.

The WTRU may be configured with multiple RSs that are contained indifferent sub-bands of a given BWP. The WTRU may choose an RS from asub-band (e.g., with the least interference) to perform RLM. Differentparts of the BWP may experience different interferences, for example, ifcompeting nodes use non-equal BWP.

The WTRU may be configured with a large set of RLM-RSs. The WTRU may beconfigured to select a subset of the RLM-RSs, for example, based on somepre-defined rules.

The WTRU may select a subset of resources from the large configured setof resources to monitor. For example, the WTRU may randomly select at aT_(period_interval) (e.g., each T_(period_interval)) a subset ofresources to monitor. The effect of interference may be randomized, forexample, if it is assumed that spectrum occupation from neighboringnodes and/or CCA from the gNB follow a uniform distribution.

Configured RLM resources (e.g., each configured RLM resource or aconfigured set of RLM resources) may be associated with a certainmonitoring periodicity. The WTRU may be configured to monitor resources(e.g., each resource) for a predefined time period. Diversity in thelink monitoring may be introduced. Not transmitting RSs for a longperiod of time may not impact the reliability of the IS and/or OOSindications.

The presences of hidden nodes may be determined. A WTRU may beconfigured to perform CCA (e.g., measure RSSI threshold) in one or morepredefined time windows (e.g., occurring at a preconfiguredperiodicity). The WTRU may receive the results of a CCA that isperformed by the network during the same predefined time window and/orperiodicity. The WTRU may receive the results in a broadcast message(e.g. SIB) or dedicated RRC signaling. The WTRU may compare the resultsof local channel sensing (e.g. CCA at the WTRU) and remote channelsensing (e.g. CCA at the network). The WTRU may determine whether thereare one or more hidden nodes based on the comparison. The WTRU maydetermine that there are one or more hidden nodes if the local andremote CCA results do not match. The WTRU may be further configured totrigger a report indicating the presence of hidden nodes (e.g. when themismatch of CCA results occur) to the network. The report may be via aRRC message or measurement report. The WTRU may consider the results ofthe determination whether there are hidden nodes to perform channelstatus aware RLM (e.g., as described herein).

1-20. (canceled)
 21. A wireless transmit/receive unit (WTRU),comprising: a processor configured to: perform a listen before talk(LBT) procedure associated with a first bandwidth part (BWP) of aserving cell; determine a BWP failure associated with the first BWP ofthe serving cell, wherein the BWP failure is determined based on anumber of LBT failures associated with the first BWP of the servingcell; perform a LBT procedure associated with a second BWP of theserving cell; determine that the LBT procedure associated with thesecond BWP of the serving cell is successful; and perform a randomaccess procedure associated with the second BWP of the serving cell. 22.The WTRU of claim 21, wherein the processor is further configured tosend, to a base station, information that indicates the BWP failureassociated with the first BWP of the serving cell.
 23. The WTRU of claim21, wherein the first BWP of the serving cell is active at a first time,the number of LBT failures associated with the first BWP of the servingcell is equal to or greater than a preconfigured value, and the secondBWP of the serving cell is active at a second time, wherein theprocessor is further configured to determine that a number of LBTfailures associated with the second BWP of the serving cell is less thanthe preconfigured value.
 24. The WTRU of claim 23, wherein the servingcell comprises a plurality of BWPs, and the first BWP is an initial BWPof the plurality of BWPs and inactive at the second time.
 25. The WTRUof claim 21, wherein the BWP failure associated with the first BWP ofthe serving cell is determined based on a counter that counts the numberof LBT failures associated with the first BWP of the serving cell. 26.The WTRU of claim 25, wherein the processor is further configured toincrement the counter based on a LBT failure of the number of LBTfailures associated with the first BWP of the serving cell.
 27. The WTRUof claim 21, wherein the number of LBT failures associated with thefirst BWP is equal to or greater than a maximum value.
 28. A method,comprising: performing a listen before talk (LBT) procedure associatedwith a first bandwidth part (BWP) of a serving cell; determining a BWPfailure associated with the first BWP of the serving cell, wherein theBWP failure is determined based on a number of LBT failures associatedwith the first BWP of the serving cell; performing a LBT procedureassociated with a second BWP of the serving cell; determining that theLBT procedure associated with the second BWP of the serving cell issuccessful; and performing a random access procedure associated with thesecond BWP of the serving cell.
 29. The method of claim 28, furthercomprising sending, to a base station, information that indicates theBWP failure associated with the first BWP of the serving cell.
 30. Themethod of claim 28, wherein the first BWP of the serving cell is activeat a first time, the number of LBT failures associated with the firstBWP of the serving cell is equal to or greater than a preconfiguredvalue, and the second BWP of the serving cell is active at a secondtime, wherein the method further comprising determining that a number ofLBT failures associated with the second BWP is less than thepreconfigured value.
 31. The method of claim 30, wherein the servingcell comprises a plurality of BWPs, and the first BWP is an initial BWPof the plurality of BWPs and inactive at the second time.
 32. The methodof claim 28, wherein the BWP failure associated with the first BWP ofthe serving cell is determined based on a counter that counts the numberof LBT failures associated with the first BWP of the serving cell. 33.The method of claim 32, further comprising incrementing the counterbased on a LBT failure of the number of LBT failures associated with thefirst BWP of the serving cell.
 34. The method of claim 28, wherein thenumber of LBT failures associated with the first BWP is equal to orgreater than a maximum value.